Plasmonic blackbody: Almost complete absorption of light in nanostructured metallic coatings

We have experimentally demonstrated blackbodylike behavior in a thin nanostructured metallic layer shaped in the form of a composite deep diffraction grating. This behavior is recorded over a wide optical wavelength range (240–550 nm) and for a broad range of angles of light incidence $\left(0–75°\right)$ for samples with metal thickness of just 90 nm. The strong absorption at a level of 97–99% is observed for one light polarization and is attributed to excitation of localized plasmons coupled to incident light waves. We show that the studied structures exhibit anomalies which consist in disappearance of reflection for both $p$- and $s$-polarized light at corresponding “Brewster” angles. An effective-medium approach provides a satisfactory qualitative description of the reflection and transmission spectra in our samples and confirms their blackbody behavior.